The present invention relates to fluidic injection systems for use with combustion engines, and more particularly to fluidic injection assemblies for controlled injection of fluid relative to an exhaust nozzle of a gas turbine engine.
In order to implement an augmented gas turbine engine cycle, a variable area nozzle is generally required to provide proper engine backpressure and flow matching throughout an operational range. Variable geometry nozzles for aircraft engines are well-known in the art as a means for providing nozzle throat area control and nozzle exit area control. These systems use mechanically actuated deflectors or other mechanical structures to control physical nozzle area characteristics. Some variable geometry nozzles can also provide thrust vectoring, that is, controllable deflection of exhaust gas flow. However, mechanical complexity, restrictive geometry options, weight and maintenance demands are significant requirements for most variable geometry nozzle designs.
Fluidic injection systems used with fixed geometry nozzles are an alternative to variable geometry designs. These fluidic injection systems utilize engine bleed air directed to the engine nozzle to control an effective nozzle area. For example, Koshoffer, U.S. Pat. No. 6,336,319, discloses non-combusting fluidic injection system for a gas turbine engine nozzle, which utilizes compressor bleed air injected directly into the nozzle area without any combustion process to further pressurize the bleed air. Hunter et al., U.S. Pat. No. 6,758,032, discloses a pulse detonation fluidic injection system for a gas turbine engine nozzle. Hunter et al. discloses the use of compressor bleed air by the pulse detonation fluidic injection system, and seeks uniform and non-turbulent fluidic injection flows. Hunter et al. utilizes pulse detonation waves that are distinguished from deflagration combustion processes.
However, known fluidic injection systems have opportunities for improvement. Many require excessive engine bleed flows, which presents an undesirable performance drawback. Compressor bleed air is “expensive” air, and combustion nozzle fluidic injection system that utilize compressor bleed air present a particularly undesirable drain on engine efficiency by decreasing the mass of the primary gas turbine engine flow. Moreover, existing designs are often relatively large and heavy.
It is desired to provide a relatively light and compact combustion nozzle fluidic injection apparatus that has minimal bleed air requirements.